(a) Field of the Invention
The present invention relates to a particulate matter sensor and a measuring method thereof, and more particularly, to a particulate matter sensor that compares a capacitance value of a reference electrode, which is constantly maintained, and a capacitance value of a main electrode, which is varied by particulate matter so as to strongly correspond to external noise and environmental changes.
(b) Description of the Related Art
Recently, as exhaust gas regulations of vehicles have been strengthened, attention to a post-processing apparatus for purifying exhaust gas has increased.
Particularly, as a diesel engine vehicle generates an exhaust flow including particulate matter (PM) of a varying amount, the diesel engine vehicle is known to be a major cause of air pollution such that regulations thereof are becoming more stringent.
To reduce the particulate matter of the diesel vehicle, a diesel particulate filter (DPF) is applied to the exhaust gas, and a particulate matter sensor is used to sense an amount of particulate trapped in the diesel particulate filter.
The particulate matter sensor detects changes of resistance or capacitance generated as the particulate matter included in the exhaust is accumulated, and is installed at the rear end of the diesel particulate filter in an exhaust system.
Methods of operating the particulate matter sensor may be classified into an accumulation method and a real-time method.
The particulate matter sensor of the accumulation method used in most vehicles senses a change of current flow as the particulate matter is accumulated on two digital electrodes applied with voltages.
The particulate matter sensor of the accumulation method has a simple structure such that its reliability is high and its manufacturing cost is low, thereby being appropriate for used in a vehicle.
However, an initial cumulative time is required until the change signal of the current flow is generated in the particulate matter sensor of the accumulation method.
On the other hand, in the particulate matter sensor of the real-time method, the amount of the particulate matter is monitored in real time by detecting an ionization reaction of the particulate matter.
However, the particulate matter sensor of the real time method has low accuracy and a size that is bulky such that it is difficult to be downsized.
Accordingly, research on a particulate matter sensor that accurately and rapidly measures the particulate matter in the exhaust gas of the exhaust system is required.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.